Wood fibre based direct pressed laminated flooring (DPL) usually comprises a core of a 6-12 mm fibre board, a 0.2 mm thick upper decorative surface layer of laminate and a 0.1-0.2 mm thick lower balancing layer of laminate, plastic, paper or like material.
The surface layer of a laminate floor is characterized in that the decorative and wear properties are generally obtained with two separate layers one over the other. The decorative layer is generally a printed paper and the wear layer is a transparent overlay paper, which comprises small aluminium oxide particles.
The printed decorative paper and the overlay are impregnated with melamine resin and laminated to a wood fibre based core under heat and pressure. The balancing layer is used to keep the panel flat after production and when the panel is exposed to variations in moisture conditions that cause the surface layer to swell and shrink.
Recently new “paper free” Wood Fibre Floor (WFF) types have been developed with solid surfaces comprising a substantially homogenous mix of fibres, binders and wear resistant particles.
The new “paper free” WFF floors with a solid surface comprising a homogenous mix of fibres, preferably wood fibres, small hard wear resistant particles and a binder are produced according to a production method wherein the WFF mix is applied in powder form on a core. The wood fibres are generally refined, mechanically worked, and of the same type as used in HDF and particleboard, i.e. treated in a way that the lignin content is essentially unchanged. The wood fibres comprise natural resins such as lignin. The wear resistant particles are preferably aluminium oxide particles. Other suitable wear resistant materials are for example silica or silicon carbide. The surface layer comprises preferably also colour pigments and/or other decorative materials or chemicals. Processed fibres e.g. bleached wood fibres may also be used. Processed fibres may be semi-transparent, and are preferably transparent in a cured binder.
The binder is preferably a thermosetting resin such as amino resins, for example melamine or urea formaldehyde resin. Any other binder, preferably synthetic thermosetting or thermoplastic resins, may be used.
The WFF layer is generally scattered in dry powder form on a wood based core, such as for example HDF. The layer is cured under heat and pressure to a 0.1-1.0 mm solid layer.
Several advantages over known technology and especially over conventional laminate floorings can be obtained:
The wear resistant surface layer, which is a homogenous mix, can be made much thicker compared to conventional laminate surface layers and a wear resistance is achieved, which is considerably higher.
New and very advanced decorative effects can be obtained with deep embossing and by separate decorative materials, which can be incorporated into the homogenous surface layer and coordinated with the embossing.
An increased impact resistance can be reached with a homogenous surface layer, which is thicker and has a higher density.
The homogenous surface layer can comprise particles that have a positive impact on sound and moisture properties.
Production costs can be reduced since low cost and even recycled materials can be used and several production steps can be eliminated.
In WO 2009/065769, a separate wood fibre layer of the above described WFF type is disclosed, which may be used as a separate surface layer. The layer is cured by applying heat and pressure such that a separate layer is formed. However, handling of this type of separate layer has proven to be difficult, since the cured layer becomes brittle and difficult to handle without being damaged.